A computer system that boots up from a SAN (storage area network), (the computer system in a SAN environment) has been known. In the computer system in the SAN environment, each server reads a program such as an OS (Operating System) from an external disk apparatus, which is a storage, through the SAN. Thereby, each server is booted up.
In the computer system in the SAN environment, to improve the reliability of the computer system, when a fault occurs in one server (active computer) for example, another server (stand-by computer) continues to execute a job of the server with the fault. That is, the server has redundancy.
In the redundant computer system in the SAN environment, for the same purpose, even when the fault occurs in a network switch and the external disk apparatus constituting the SAN, the stand-by computer is adapted to be able to continue the job of the active computer (refer to Japanese Laid-Open Patent Publication No. 2007-293422).
The reliability of the computer system in the SAN environment is improved by means of a variety of configurations. However, as described above, while various considerations have been made for the fault in the server (managed server), the network switch, and the external disk apparatus, the consideration is not made for the fault in a management server (boot server).
That is, even in the redundant computer system in the SAN environment, a hardware fault or a software fault may occur in the management server. According to the study by the present inventor, since the managed server in this case can not obtain a WWN (World Wide Name) value, or a unique ID, from the management server, the managed server can not set a WWN value in an HBA (Host Bus Adapter) of the managed server. Thus, the managed server cannot boot the program such as the OS (Operating System) from the storage through the SAN.